"Windows, for some time now, has really been a DRM platform, restricting you from making copies of digital files," said executive director Peter Brown. And if Microsoft's Trusted Computing technology were fully implemented the way the company would like, the vendor would have "malicious and really complete control over your computer."

The group, best-known for overseeing the General Public License (GPL) used by most open-source software, including Linux, will hold a rally at noon in Boston Common, where it will unveil a 12-foot-tall art installation depicting Windows 7 "being trashed," Brown said.

The group is also sending a letter (available at the group's Web site) to top executives at Fortune 500 companies that argues their companies would benefit ethically, technically and, in the long-term, financially, from switching away from Windows and Microsoft Office to free alternatives such as Linux and OpenOffice.org.

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Founded in the mid-1980s by hacker-activist Richard Stallman, the FSF argues that free software and source code is a moral right. It takes pains to distinguish itself from the open-source movement, which advocates sharing of source code but tolerates charging for software.

Both groups, however, view proprietary software vendors such as Microsoft, Adobe Systems Inc., and Apple Inc. as the enemy, Brown said.

Even with DRM, users running Windows PCs still maintain more freedom and privacy than those who use cloud computing services such as Google Docs and store their data there, Brown said.

"That is the ultimate giving-away of your freedom," he said. "That's not a software freedom issue, it's a stupidity issue."

While Brown acknowledges that many Fortune 500 companies base their businesses around proprietary business models similar to Microsoft, he also points out that most of them, at least regarding software, are more consumer than vendor.

"Large corporations spend an awful lot of money on software. They face numerous software audits and more vendor lock-in than you or me," Brown said. "Do you think they would rather be driving on a freeway, or always be paying on toll roads?"

"I'm not expecting an instant wave of companies switching off XP to Linux," he said. "But we would like get that debate going. Hopefully, some will re-evaluate and say no to Windows 7."